Preheat oven to 350 degrees. Grease and flour two 9-inch cake pans. Sift together the flour, baking powder, baking soda, salt and cinnamon. Set aside. In a large bowl, mix together the sugar and eggs until thick and pale. Stir in the oil, then gradually mix in the sifted dry ingredients. Fold in the carrots and nuts. Spread evenly into the prepared pans. Bake for 35 minutes, or until a toothpick inserted into the cake comes out clean. When cool, frost with your favorite cream cheese or butter cream frosting.